Insulated lead frame for integrated circuits and method of manufacture thereof

Abstract

An insulated lead frame is disclosed. The preferred embodiment contains a lead over chip lead frame having an aluminum oxide insulator on portions of the power supply busses where no electrical connections will be made. The aluminum oxide may be easily deposited by an arc deposition process such as by plasma deposition. A mask prohibits the aluminum oxide from coating the places on the power supply busses where electrical connection, such as by wire bond, will be made. Wire bonds crossing over the power supply busses as they connect bond pads to the lead fingers of the lead frame are therefore less likely to short to the insulated power supply busses. A semiconductor packaged device having an aluminum oxide coating to the underside of the chip support pad is also disclosed. The aluminum oxide coating promotes adhesion between the chip support pad and the encapsulant, that is typically plastic, thereby preventing the chance of delamination and package cracking.

What is claimed is: 
     
       1. An insulated lead frame, comprising: a first plurality of conductive lead fingers;   a second plurality of conductive lead fingers;   a first power supply bus lying between the first and second pluralities of conductive lead fingers;   a second power supply bus lying between the first and second pluralities of conductive lead fingers, adjacent to the first power supply bus; and   an aluminum oxide insulator on selected portions of the first power supply bus and on selected portions of the second power supply bus, the selected portions of the first and second power supply busses having no electrical connection made to them.   
     
     
       2. The insulated lead frame of claim 1 wherein the aluminum oxide is plasma arc deposited. 
     
     
       3. The insulated lead frame of claim 1 wherein the aluminum oxide is flame spray deposited. 
     
     
       4. A semiconductor packaged device, comprising: a semiconductor integrated circuit chip having an active face and a plurality of centrally located bonding pads on its active face;   a lead frame overlying the active face of the semiconductor integrated circuit chip having a plurality of lead fingers and having at least two power supply busses;   a plurality of wire bonds, some that cross over a power supply bus for connecting some of the centrally located bonding pads to some of the plurality of lead fingers, and some that connect other of the centrally located bonding pads to the power supply busses;   an encapsulant, encapsulating the semiconductor integrated circuit chip, the .plurality of wire bonds, and the lead frame such that portions of the plurality of lead fingers extend through the encapsulant so that external electrical connections may be made to the semiconductor integrated circuit chip; and   an aluminum oxide dielectric coating on the power supply busses where some of the plurality of wire bonds cross over the power supply busses when connecting some of the centrally located bonding pads to some of the plurality of lead fingers.   
     
     
       5. The packaged device of claim 4 wherein the dielectric coating of aluminum oxide is about .001 inches thick. 
     
     
       6. The packaged device of claim 4 wherein the dielectric coating of aluminum oxide is between the range of about 0.0005 to 0.05 inches thick. 
     
     
       7. The packaged device of claim 4 wherein the aluminum oxide has a roughened surface. 
     
     
       8. The packaged device of claim 7 wherein the roughened surface of the aluminum oxide has a RMS of about 130 micrometers. 
     
     
       9. The packaged device of claim 4 wherein the aluminum oxide is arc deposited by plasma deposition. 
     
     
       10. The packaged device of claim 4 wherein the aluminum oxide is arc deposited by flame spray deposition. 
     
     
       11. An insulated lead frame comprising: a first plurality of conductive lead fingers;   a second plurality of conductive lead fingers;   a power supply bus lying between the first and second pluralities of conductive lead fingers; and   a ceramic insulator on selected portions of the power supply bus, the selected portions of the power supply bus having no electrical connection made to them.   
     
     
       12. The insulated lead frame of claim 11 wherein the ceramic insulator is an oxide. 
     
     
       13. The insulated lead frame of claim 12 wherein the oxide is aluminum oxide. 
     
     
       14. An encapsulated semiconductor device, comprising: a semiconductor die having a plurality of terminals thereon disposed within an encapsulating material;   a lead frame having a plurality of lead fingers and a power supply bus connected to one of the plurality of lead fingers disposed within the encapsulating material, and having portions of the plurality of lead fingers extending out of the encapsulating material;   a means for connecting some of the plurality of lead fingers to some of the plurality of terminals of the semiconductor die that crosses over the power supply bus and is disposed within the encapsulant; and   a ceramic insulator on the power supply bus where the means for connecting some of the plurality of lead fingers to some of the plurality of terminals crosses over the power supply bus.   
     
     
       15. The encapsulated semiconductor device of claim 14 wherein wire bonds comprise the means for connecting some of the plurality of lead fingers to some of the plurality of terminals of the semiconductor die. 
     
     
       16. The encapsulated semiconductor device of claim 14 wherein the insulator is aluminum oxide which is deposited onto the power supply bus. 
     
     
       17. A semiconductor device, comprising: a semiconductor integrated circuit chip with a terminal thereon;   a lead finger;   a metal strip lying between the terminal of the semiconductor integrated circuit chip and the lead finger;   a ceramic insulator coating on a portion of the metal strip; and   a connecting means for connecting the terminal to the lead finger, the connecting means disposed over the ceramic insulator coating.